Since the 4.7L is a smaller engine and has less torque than the hemi, higher numerical gearing is a way to compensate and make up for this. It's like riding a multi speed mountain bike, if you are in a low gear it is extremely easy to pedal at low speeds, but is very hard to go fast, but if you are in a high gear it is extremely difficult to pedal at low speeds but very easy to go fast. The 4.7L is more of a high revving engine, so it makes some sense to have higher numerical gearing vs the hemi, but IMO 4.56 is too much (depending on tire diameter). I would like to go to 4.56, but I think it'd kill my mpg.
Gearing is a way of torque multiplication. If you have 100 lb ft of torque at the rear of the transmission and have 3.55 gearing then you have 355 lb ft of torque at the wheels. By simply changing to 4.56 gears you now have 456 lb ft of torque at the wheels...